1. Field of the Invention
The present invention relates to a method and system for transferring group invitee information to a receiving-side Push-To-Talk (PTT)-over-Cellular (PoC) client upon establishing an ad-hoc PoC group session in a PoC system.
2. Description of the Related Art
Significant developments in mobile communication technology and the expansion of communication networks have led to the provision of various services and applications which use mobile telephones. In addition to the basic communication service, users are demanding more diversified services, including a positioning, a multimedia and a PTT service. Particularly, the PTT service supports various supplementary functions such as instant messenger and status display, as well as group and voice communication which have been provided by conventional radio transmitters or Trunked Radio Systems (TRSs).
Currently, the industry is working to standardize a PoC service which employs such a PTT function in a mobile communication network. One feature of the PoC service, which draws a distinction between the PoC service and the conventional mobile communication service, is that a user can perform communication while moving between sessions, if necessary, because he/she belongs to a plurality of sessions. The requirements that a user must be able to communicate while moving among a plurality of PoC sessions are specified in the Open Mobile Alliance (OMA) which is an organization regulating pertinent mobile communication services.
According to the PoC 1.0 standard, a PoC session is established in such a manner that media data is transmitted only to PoC clients participating in the PoC session in real time. According to such a rule, users not participating in the PoC session due to battery discharge or absence, for example, cannot receive a media stream, such as voice, transmitted in a one-to-one session or group PoC session. That is, the PoC 1.0 technology does not support a voice mail box function, which has been supported in conventional communication systems.
Meanwhile, the PoC 1.0 standard supports an ad-hoc group session mode which appoints a user list as an object group. In this case, since each receiving-side PoC client cannot receive information about users invited to an ad-hoc group session, there is a problem in that each receiving-side PoC client has to participate in the ad-hoc group session before obtaining information about the invited users. For this reason, a scheme for transferring information about all users invited to an ad-hoc group session as described above, which is required for receiving-side users to determine whether to participate in the session, to the receiving-side users upon inviting the receiving-side users to the session is specified as a requirement in PoC 2.0.
Meanwhile, the PoC 1.0 standard supports a pre-established session and an auto-answer mode so as to simplify a session establishment procedure. When a PoC client and a PoC server, which support both a pre-established session and an auto-answer mode as described above, receive a session invitation message for the ad-hoc group session, the PoC client and PoC server respond immediately without confirmation of each corresponding user by transmitting a session participating success message to a transmitting-side PoC network. This is because, when the PoC server directly transmits a Session Initiation Protocol (SIP) success message as a response, an SIP message exchange procedure between the receiving-side PoC server and PoC client is simplified and thus a session setup time is reduced. However, the pre-established session and auto-answer mode provided in the prior art have disadvantages in that it is impossible to provide a message for transferring group invitee information upon establishing the ad-hoc group session, or to request a receiving-side PoC user to confirm invitee information.